Recently, display devices and lighting devices have been required to be, for example, lightweight, thin, highly efficient, and eco-friendly. To satisfy these requirements, studies into the use of organic light-emitting devices (OLEDs) have been actively undertaken.
OLEDs may be divided into single OLEDs, each of which has a single organic light-emitting layer, and tandem OLEDs, each of which has two or more organic light-emitting layers stacked on each other in series. Tandem OLEDs may be used in display devices or lighting devices requiring a high level of luminance and a longer lifespan due to higher reliability and longer lifespans thereof, as compared to single OLEDs.
A white OLED has different organic light-emitting layers between an anode and a cathode, to emit different colors of light. A charge generation layer is disposed between the organic light-emitting layers.
However, conventional charge generation layers lower and reduce the power efficiencies and lifespans of OLEDs due to high driving voltages thereof, which may be problematic.